How I think each returnee may influence the dynamic.
JACKIE:
Jackie returning will escalate into one of two things: it will either unite an Austwins/Goblins F6 to take out Vanessa and Steve, or it'll force Jackie/James/Meg to turn on Austwins. And since Jackie seems to have a functioning brain, I'm leaning toward the latter. Even though Austwins are under the impression that Jackie would work with them, I don't think they wouldn't take a strike at Jackie/James/Meg if they themselves were in power, especially with Vanessa in their ear. The big downside to Jackie returning is that it'll increase the target on her/James/Meg and make them easy nominations in the event anyone else wins HOH. Steve should go after the Austwins but Jackie returning will create another trio on the other side of the house so Steve's choices will be rather limited and I assume he'd stick with the Austwins to dwindle down the other side again. Jackie or one of her allies need HOH or she's probably out.
BECKY:
Becky returning will be like a down-graded Jackie. Becky has the potential, rather than the sure-fire guarantee to turn James and Meg against Austwins. James & Meg will have to choose between Austwins and Becky, and that choice will only matter if either of them were to win HOH. If Austwins won HOH, Becky would be out. Becky could use Steve and Vanessa as leverage, but she has a very shaky relationship with Vanessa which I doubt can be easily repaired in only a week. Becky could potentially buy herself safety with a Vanessa or Steve HOH, but I don't know whether they'd trust her enough to not team back up with James and Meg down the line, even though that fear would be far less prevalent than it would with Jackie back in the game, which is the one major upside of a Becky return.
SHELLI:
In my mind, Shelli is still a complete wildcard. She definitely has Steve waiting for her, and potentially Vanessa. I think Shelli would actually be foolish to target Vanessa. Ideally, Shelli/Steve/Vanessa form a Final 3, knowing that Austin has the twins and vice versa. If Shelli were to win HOH, it's a toss-up. She should go after one of Austwins before targeting James and/or Meg, but I'm hoping she's not blinded by her James hatred to see rationally. If Shelli were to take out an Austwin, there's a very good chance the two survivors would team up with James and Meg, making it 4 vs. 3 in their favor, which is not a good scenario for Shelli. And at the end of the day, a Shelli return would be great news for Vanessa as Shelli will be a giant shield for her.
JOHN:
A John return would be similar to a Shelli return barring HOH wins. Ideally, he makes a F3 with Steve and Vanessa. John will probably be the target for Austwins, and potentially James/Meg (if not Vanessa). However, John may have more leverage with James and Meg than Shelli would, even though James/Meg would still likely lean toward working with Austwins. John would be in desperate need for HOH but his next best choices would be Steve or Vanessa. In that case, similarly to Shelli, John can have some influence in whether Austwins or James/Meg are targeted but at the end of the day, he will be a shield for Vanessa, but a much smaller shield to keep in mind.
